Single-mix refrigerant LNG production process

Abstract

A simple and efficient single mixed refrigerant process for cooling and liquefying hydrocarbon feed streams such as natural gas. The process employs a closed loop single mixed refrigerant process for cooling duty. Refrigerant compressed to high pressure using at least three stages of compression and two intercoolers, both producing liquid. A hydraulic turbine is used to expand the high pressure refrigerant before it flows into the main heat exchanger.

Claims

1. A method for liquefying a hydrocarbon stream using a mixed refrigerant, (a) Cooling and condensing the hydrocarbon stream and cooled two-phase high-pressure refrigerant stream in the main heat exchanger with respect to the expanded refrigerant stream so as to form a liquefied hydrocarbon stream, a condensed refrigerant stream, and a vaporized refrigerant stream, (b) Compressing the vaporized refrigerant stream in the first compression step to a first pressure so as to form a low-pressure compressed refrigerant stream, (c) Cooling the low-pressure compressed refrigerant stream in a first ambient cooler so as to form a cooled two-phase refrigerant stream, (d) Separating the cooled two-phase refrigerant stream into a first cooled vapor stream and a first cooled liquid stream, (e) Compressing the first cooled steam stream to a second pressure in the second compression step so as to form an intermediate pressure compressed stream, (f) Cooling the intermediate pressure compression stream in a second ambient cooler so as to form a cooled intermediate pressure compression stream, (g) Separating the cooled medium-pressure compression stream into a second cooled vapor stream and a second cooled liquid stream, (h) Compressing the second cooled steam stream in the third compression stage to a third pressure so as to form a two-phase high-pressure compression stream, (i) Cooling the first two-phase high-pressure stream, including the two-phase high-pressure compression stream, in a third ambient cooler so as to form a cooled two-phase high-pressure compression stream, (j) Expanding the condensed refrigerant stream to form the expanded refrigerant stream, wherein at least a portion of the expansion is carried out using a hydraulic turbine. (k) Combining the first cooled liquid stream with a fluid stream located downstream of the cooled two-phase refrigerant stream and upstream of the cooled two-phase high-pressure compression stream, (l) Combining the second cooled liquid stream with a fluid stream located downstream of the cooled two-phase refrigerant stream and upstream of the cooled two-phase high-pressure compression stream, (n) A method comprising reducing the pressure of the second cooled liquid stream to the first pressure before performing step (l).

2. The method according to claim 1, further comprising changing the pressure of the first cooled liquid stream before performing step (k).

3. The method according to claim 2, wherein step (m) includes increasing the pressure of the first cooled liquid stream to the second or third pressure before performing step (k).

4. The method according to claim 1, wherein the expanded refrigerant stream provides the sole cooling duty for step (a).

5. The method according to claim 1, wherein the flow of refrigerant in steps (a) to (n) defines a closed-loop cooling cycle, and all of the refrigerant in the vaporized refrigerant stream circulates through steps (a) to (n) and flows through the hydraulic turbine in step (j).

6. The method according to claim 5, wherein the main heat exchanger comprises a warm end and a cold end, and the expanded refrigerant stream is introduced into the main heat exchanger at the cold end.

7. The method according to claim 1, wherein the vaporized refrigerant stream has a first flow rate in step (b), and the expanded refrigerant stream has a second flow rate in step (n), and the first flow rate is equal to the second flow rate.

8. The method according to claim 1, wherein the cooled two-phase high-pressure refrigerant stream has a pressure of at least 1000 PSIA (68.95 bara).

9. The method according to claim 1, wherein the composition of the refrigerant in the vaporized refrigerant stream, the two-phase high-pressure refrigerant stream, the condensed refrigerant stream, and the expanded refrigerant stream is the same.

10. A method for liquefying a hydrocarbon stream using a mixed refrigerant, (a) Cooling and condensing the hydrocarbon stream and cooled two-phase high-pressure refrigerant stream in the main heat exchanger with respect to the expanded refrigerant stream so as to form a liquefied hydrocarbon stream, a condensed refrigerant stream, and a vaporized refrigerant stream, (b) Compressing the vaporized refrigerant stream in the first compression step to a first pressure so as to form a low-pressure compressed refrigerant stream, (c) Cooling the low-pressure compressed refrigerant stream in a first ambient cooler so as to form a cooled two-phase refrigerant stream, (d) Separating the cooled two-phase refrigerant stream into a first cooled vapor stream and a first cooled liquid stream, (e) Compressing the first cooled vapor stream to a second pressure in the second compression step so as to form an intermediate pressure refrigerant stream, (f) Pumping the first cooled liquid stream to the second pressure so as to form a pumped first cooled liquid stream, (g) Combining the pumped first cooled liquid stream with the intermediate pressure refrigerant stream to form a combined intermediate pressure refrigerant stream, (h) Cooling the combined medium-pressure refrigerant stream in a second ambient cooler so as to form a cooled combined medium-pressure refrigerant stream, (i) Separating the cooled combined medium-pressure refrigerant stream into a second cooled vapor stream and a second cooled liquid stream, (j) Compressing the second cooled steam stream in the third compression step to a third pressure so as to form a high-pressure compressed stream, (k) Pumping the second cooled liquid stream to the third pressure so as to form a pumped second cooled liquid stream, (l) Combining the pumped second cooled liquid stream with the high-pressure compressed stream to form a two-phase high-pressure refrigerant stream, (m) Cooling the two-phase high-pressure refrigerant stream in a third ambient cooler so as to form the cooled two-phase high-pressure refrigerant stream, (n) Expanding the condensed refrigerant stream through a hydraulic turbine to form the expanded refrigerant stream, The main heat exchanger comprises a warm bundle and a cold bundle, and the method is (o) When performing step (a), provide a first cooling duty within the warm bundle, (p) A method further comprising providing a second cooling duty within the cold bundle when performing step (a), wherein the second cooling duty is less than the first cooling duty.

11. The method according to claim 10, wherein the expanded refrigerant stream provides the sole cooling duty for step (a).

12. The method according to claim 10, wherein the flow of refrigerant in steps (a) to (n) defines a closed-loop cooling cycle, and all of the refrigerant in the vaporized refrigerant stream circulates through steps (a) to (l) and flows through the hydraulic turbine in step (n).

13. The method according to claim 12, wherein the main heat exchanger comprises a warm end and a cold end, and the expanded refrigerant stream is introduced into the main heat exchanger at the cold end.

14. The method according to claim 10, wherein the vaporized refrigerant stream has a first flow rate in step (b), and the expanded refrigerant stream has a second flow rate in step (n), the first flow rate being equal to the second flow rate.

15. The method according to claim 10, wherein the cooled two-phase high-pressure refrigerant stream has a pressure of at least 1000 PSIA (68.95 bara).

16. The method according to claim 10, wherein the composition of the refrigerant in the vaporized refrigerant stream, the two-phase high-pressure refrigerant stream, the condensed refrigerant stream, and the expanded refrigerant stream is the same.

17. The method according to claim 10, wherein the warm bundle and the cold bundle are each contained within separate shells.

18. The main heat exchanger further comprises an intermediate bundle, and the method is (q) The method of claim 10, further comprising providing a third cooling duty in the intermediate bundle when performing step (a), wherein the third cooling duty is less than the first cooling duty.

19. The method according to claim 18, wherein the warm bundle, the cold bundle, and the intermediate bundle are each contained within a separate shell.

20. The method according to claim 10, wherein the hydrocarbon stream includes natural gas.

21. The method according to claim 10, further comprising the step (r) of selectively expanding the condensed refrigerant stream through an expansion valve located on a bypass circuit instead of through the hydraulic turbine.

22. A method for liquefying a hydrocarbon stream using a mixed refrigerant, (a) Cooling and condensing the hydrocarbon stream and cooled two-phase high-pressure refrigerant stream in the main heat exchanger with respect to the expanded refrigerant stream so as to form a liquefied hydrocarbon stream, a condensed refrigerant stream, and a vaporized refrigerant stream, (b) Expanding the condensed refrigerant stream to form the expanded refrigerant stream, wherein at least a portion of the expansion is carried out using a hydraulic turbine. (c) Compressing the vaporized refrigerant stream in the first compression step to a first pressure so as to form a low-pressure compressed refrigerant stream, (d) Cooling the low-pressure compressed refrigerant stream in a first ambient cooler so as to form a cooled two-phase refrigerant stream, (e) The expanded cooled stream is combined with the cooled two-phase refrigerant stream, and the combined cooled two-phase refrigerant stream is separated into a first cooled vapor stream and a first cooled liquid stream, (f) Compressing the first cooled steam stream to a second pressure in the second compression step so as to form an intermediate pressure compressed stream, (g) Pumping the first cooled liquid stream to a third pressure so as to form a pumped first cooled liquid stream, (h) Cooling the intermediate pressure compression stream in a second ambient cooler so as to form a cooled intermediate pressure compression stream, (i) Separating the cooled medium-pressure compression stream into a second cooled vapor stream and a second cooled liquid stream, (j) Compressing the second cooled steam stream in the third compression stage to the third pressure so as to form a two-phase high-pressure compression stream, (k) Combining the pumped first cooled liquid stream with the two-phase high-pressure compression stream to form a combined two-phase high-pressure compression stream, (l) Cooling the combined two-phase high-pressure compression stream in a third ambient cooler so as to form the cooled two-phase high-pressure compression stream, (m) Expanding the second cooled liquid stream through an expansion valve to form the expanded cooled stream and reducing the pressure to the first pressure, (n) A method comprising combining the expanded cooled stream with the cooled two-phase refrigerant stream to form the combined cooled two-phase refrigerant stream.

23. The method according to claim 22, wherein the expansion in step (b) is provided by a hydraulic turbine, followed by an expansion valve.

24. The method according to claim 22, wherein the second compression step is performed at a temperature of approximately 96.8°F.

25. The method according to claim 22, wherein the expanded refrigerant stream provides the sole cooling duty for step (a).

26. The method according to claim 22, wherein the flow of refrigerant in steps (a) to (n) defines a closed-loop cooling cycle, and all of the refrigerant flows through the hydraulic turbine in step (l).

27. The method according to claim 22, wherein the main heat exchanger comprises a warm bundle and a cold bundle contained within a separate shell.

28. The method according to claim 27, wherein the main heat exchanger further comprises an intermediate bundle located between the warm bundle and the cold bundle.

29. The method according to claim 22, wherein the hydrocarbon stream includes natural gas.

30. The method according to claim 22, wherein the main heat exchanger comprises a warm end and a cold end, and the expanded refrigerant stream is introduced into the main heat exchanger at the cold end.

Images